Engineering News

Scientists are striving to uncover the ingenious structural engineering secrets behind the floating rafts formed by panicking fire ants.

When confronted by a sudden deluge, fire ants flee from their subterranean nests and clump together in their hundreds to form floating “rafts” which are capable of ensuring their collective survival.

These floating rafts are comprised of nothing more than the unadorned bodies of the panic-stricken ants, yet possess unique physical properties which dramatically abet their likelihood of surviving disaster.

According to scientists from the Georgia Institute of Technology, while the rafts may appear to the naked eye to be little more than chaotic balls of frenzied insects, they are true works of structural engineering brilliance.

“They’re literally building a new type of material with special properties, because of the way they connect up,” said David Hu, Assistant Professor of Mechanical Engineering at the Georgia Institute of Technology.

A study led by Paul Foster and published in The Journal of Experimental Biology in June made use of an ingenious set of methods to uncover the engineering secrets which confer the rafts with their remarkable physical and structural properties.

Instead of relying solely on the superficial observation that can be garnered from recorded footage, Foster and his team froze ant rafts in the laboratory using liquid nitrogen, and used a micro-scale computed tomography (CT) scan to analyse the 3D structure of the rafts in detail.

They discovered that what appears to be a confused jumble of formic flesh to the naked eye is actually a meticulously structure of self-organising precision and ingenuity.

The ants arrange themselves so that they are perpendicular to each other in order to maximise their usage of space and to incorporate ants of varying sizes into the structure of the raft.

Multiple scans discovered that the ants attach themselves to each other via the use of sticky pads on their limbs, with an average of 14 connections made by each ant. No fewer than 99 per cent of the ants are attached to another ant, ensuring that the responsibility of forging structural connections is equally dispersed.

The resulting structure possesses a sufficient number of air pockets, created by the spaces formed by its interlocking members, to keep the heaving mass of fleeing ants afloat.

It also possesses the additional extraordinary property of adjustable size, capable of either contracting or expanding in response to external obstacles or disturbances.

Foster’s team found that despite the ostensible complexity of the raft, the fire ants were capable of marshalling themselves into formation with surprising rapidity. When roughly a hundred ants were placed into a dry receptacle and stirred around, they still swiftly clumped together to produce a roughly raft-shaped structure despite the absence of any water.

The scientists believe the engineering accomplishments of the ants could have major safety implications for human beings, enabling us to design and build sophisticated robots which come to together to form floating rafts or bridges in the case of severe flooding disasters.